Personally, I think it is infinitely amusing that people
identified so much with this completely inanimate (and simply
constructed) object that doesn't act or emote, despite the pink hearts
emblazoned on it. People have more trouble destroying the
companion cube than killing the Little Sisters in Bioshock. It
reminds me of my cat Bünny, who has become very affectionate with
a plush cat toy that sits on my bed. She loves to snuggle with
it and knead her claws into its synthetic fur, even though it just
sits there with its dead-doll eyes, and she is purring in blissful
kitty heaven.

GLaDOS.

Portal

Portal was a brilliant game. I ordered me a plush companion
cube on their Web site after playing. The fight with GlaDOS was
so funny that I purposely died so I could hear her hilarious banter
again! -Cary